1. Field of the Invention
The present invention relates to a multicolor dye set with high water-fastness, an ink composition including the dye set, and its application in ink-jet printing.
2. Background of the Invention
Color ink for color ink-jet printing requires a wide color range and ideal color matching. A primary dye set includes cyan ink, magenta ink, yellow ink, and black ink. A secondary dye set includes other colorants obtained from matching the dyes of the primary dye set.
In fact, a successful ink composition for color ink-jet printing must meet the following requirements: good crusting resistance, good stability, proper viscosity, proper surface tension, high color saturation, little color-to-color bleed, and rapid dry time. In addition, a successful ink composition can be ejected onto plain paper without clogging.
Color can be specified by two systems: color appearance system and color mixing system. Color appearance system is a system obtained from collecting data of actual colored objects and systematically generalizing the data. Examples include the Ostwald color system, the Munsell color system, and the DIN color system. Color mixing system is based on the principle that primary colors stimulus can be matched to generate various colors. Presently, the most important color mixing system is the CIE calorimetric system, which measures color instrumentally. For example, the Munsell color system was developed by Munsell, an American painter, and is the most famous system, describing color by hue, value, and chroma. For the CIE colorimetric system, the color stimulus (stimulus X, Y, and Z) and sensation of color are caused by the incorporation of light sources, objects, and observers. Chromaticity diagram is defined by three values L*, a*, and b*. L* indicates the lightness of a color, a* the hue, and b* the chroma of a color. a* ranges from xe2x88x92a (green) to +a (red), and b* ranges from xe2x88x92b (blue) to +b (yellow). In 1976, the CIE system further incorporates hue angle (h0) and chroma (C*) (see Formula 1 and 2). In the CIELAB chromaticity diagram, color difference (xcex94E) indicates the color difference between two color samples (see Formula 3). The greater the xcex94E, the greater the color difference between two color samples. OD (optical density), also represented by absorbency, is defined by Formula 4. After a light with intensity I0 irradiates an object, the residual intensity is I.
h0=tanxe2x88x921 (b*/a*)xe2x80x83xe2x80x83Formula 1
C*=(a*2+b*2)1/2xe2x80x83xe2x80x83Formula 2
xcex94E=(xcex94L*2+xcex94a*2+xcex94b*2)1/2xe2x80x83xe2x80x83Formula 3
OD=log(Io/I)xe2x80x83xe2x80x83Formula 4
Therefore, when an ideal ink composition is used to conduct ink-jet printing, it must provide ultimate color characteristics, such as good hue and high chroma. In the present invention, the water-fastness of each ink composition is determined by evaluating AE based on Formula 3. A smaller AE indicates that the ink composition fades color to a smaller extent after water washing and has better water-fastness.
Generally speaking, if the ink for ink-jet printing includes only one colorant, it easily causes plugging at the nozzle. Therefore, many kinds of humectants are generally added. However, this easily causes a slower drying rate and poor water-fastness. For example, in U.S. Pat. No. 4,631,085 (1986), U.S. Pat. No. 4,713,113 (1987), and U.S. Pat. No. 4,737,190 (1988), the ink includes a single colorant, and a humectant is required to prevent coagulation. U.S. Pat. No. 5,925,177 (1999) discloses an ink composition including Acid Yellow 23 dye, urea, and water. The addition of urea can prevent plugging of the nozzles resulting from crystallization of the yellow dye.
The ink composition for color ink-jet printers generally includes four kinds of ink, that is, magenta ink, cyan ink, yellow ink, and black ink, which are mainly water-based dyes. In recent years, the ink composition includes six kinds of ink, that is, magenta ink, cyan ink, yellow ink, black ink, light magenta ink, and light cyan ink, or seven kinds of ink with an additional light yellow ink. The ink composition includes at least one water-based (water-soluble) dye, water, an organic solvent, and other additives. However, such dye-based water-based ink has inferior water-fastness and light resistance.
Therefore, pigment-based inks with good water-fastness and light resistance have been developed in recent years. Such ink includes at least one pigment, water, an organic solvent, and other additives. The ink-jet ink using pigment as the colorant has better water-fastness and light resistance than a dye-based ink. However, dispersants or adhesives must be added to the pigment-based ink. In addition, pigment has a larger particle size, which easily causes precipitation and coagulation, thus plugging the nozzle and negatively impacting printing properties.
One object of the present invention is to provide a water-soluble multicolor dye set with high water-fastness.
The second object of the present invention is to provide an ink composition including the above-mentioned multicolor dye set.
The third object of the present invention is to provide an ink-jet printing method using the above-mentioned ink composition.
The fourth object of the present invention is to provide a novel water-soluble magenta dye set and an ink composition including the dye set.
The fifth object of the present invention is to provide a novel water-soluble yellow dye set and an ink composition including the dye set.
To achieve the above-mentioned objects, the water-soluble multicolor dye set includes the following components:
(a) Direct Blue 199 dye and Acid Blue 9 dye;
(b) Reactive Red 180 dye, Acid Red 52 dye, and Direct Red 75 dye; and
(c) Direct Yellow 132 dye and Acid Yellow 5 dye.